Unity3D Duplicated NavMesh Agents not moving

In my scene, I have an agent which moves to a specific destination. As soon I try to duplicate it in order to create a second agent the resulting behavior is quite strange: the agents get transported to opposite corners of the map and stop moving.
Also, the navigation mesh at runtime seems altered (as you can see in the second screenshot). As soon I disable one agent the other start working as expected.

Only one active agent
Both duplicated agent active

Unity3D Duplicated NavMesh Agents not moving